Tension packer



2 Sheets-Sheet l FIG.3.

FIG.5.

INVENTORS.

.RICHARDSONJK ATTORNEY.

, JR., ET AL TENSION PACKER S E V E RO L. V|LLALON,JR. CECILR April 2, 1963 s. l.. vlLLALoN Filed July 5, 19Go FIG. l.

Aprll 2, 1963 s. l.. vxLLALoN. JR., ET AL 3,083,770

TENSION PACKER Filed July 5, 1960 2 Sheets-Sheet 2 INVENTORS. SEVERO I .VILLALON JR ATTORNEY.

FIG. 8.

H Iz

CECILPLRICHARDSONJR @J @MMM -35 c .7 BY

Severo il. Williston, Jr., and Cecil it. Richardson, lr., Dunean, Ghia., assignors to Haiiiburton Company, a corporation oi Delaware Ftied duty Een, Ser. Na. @W712i 12 Claims. (Cl. leem-1126i) The present invention is directed to a packer assembly for use in oil wells and the like and more particularly to a packer of the retrievable type. Such a packer can be employed in various well operations such as squeeze cementing, acidizing or repressuring of oil wells, etc.

During such operations it is necessary to provide a packer between the tubing or operating string and the well casing so that treating liquids such as, for example, cement, may be pumped down the tubing and pressurized without being allowed to ow up the annulus between the pipe string or tubing and the casing wall.

Most conventional packer assemblies of this nature are set by moving the operating string down once the packe is positioned at the desired depth, the packer assembly being held in place by drag springs and the like so that the operating string can be moved relative to the packer housing. Such packers require considerabie weight (which can only be afforded by the operating string) to perform the setting operation. rhe weight is needed to expand the packing element and squeezes it against the casing wall tight enough to provide a satisfactory seal in the tubing casing annulus.

However, at times it is necessary to set such packer assemblies at more shallow depths wherein the operating string or tubing is not of suiiicient length to provide the necessary weight required to perform the setting operations.

When such conditions prevail, it is necessary to provide a packer that can be set in tension, that is, instead of applying the pipe weight to set the packer, an upward strain or pull on the operating string or tubing performs the setting operations. It is obvious that such a packer being set by upward movement of the pipe string must be released by downward movement of the string.

Releasing tension packers of this nat-ure is quite simple if the operation being per-formed does not place obstacles in `the casing below the packer which prevents the operating string from being moved downwardly when it is desired to remove the packer assembly. Such a condition sometimes exists after squeeze cementing operations. The lower end or lower shoe of the packer may be entirely cemented in whereby the normal releasing operation cannot be performed due to the assembly being stuck.

It is the primary obiect of the present invention to provide a packer assembly which can be set by tension and at the same time provide means whereby the tool can be removed in case it becomes stuck or cemented in.

Brieily described, the present tool is provided with upper and lower frangible means hereinafter referred to as tension sleeves. The upper tension sleeve is designed to rupture or shear at a predetermined pull or strain and the lower tension sleeve shears at a greater predetermined pull or strain applied to it. The tool is so designed that each time a tension sleeve is sheared a portion of the `assembly can be removed from the casing and the remaining portion provides an extending neck or sleeve which can be easily engaged by a fishing or pulling tool.

The structure, operation, and advantages of the tool of the present invention will be more clearly understood by the following description taken in coniunction with the drawings in which:

FIG. l is a view partly in section or" the present device and the position assumed when the tool is being lowered into a well casing;

datati-es assaut FlG. Z is a similar view showing the assembly set in the casing with cement having been pumped through and in place below the assembly;

PEG. 3 is a fragmentary view of a portion of the device showing the J slot and lug arrangement for controlling and circulating valve of the assembly;

FG. 4 is a fragmentary view showing another slot and lug arrangement for controlling the pipe slips of the device;

FIG. 5 is a sectional view taken along the line S-S o FlG. l;

HG. 6 is a view showing the parting of the upper tension sleeve and the lower end ot the tool cemented in the casing;

HG. 7 illustrates the shearing of the lower tension sleeve and the removal of the maior portion of the as sembly; and

FiG. 8 illustrates a modiiication of the present invention.

Referring now to the drawings and particularly FEGS. l through 5, the device generally designated by the numeral `S is lowered in a casing 9 on the lower end or an operating string i8 with the parts in the position shown in PKG. l. A mandrel generally designated le composed of an upper section 12 and a lower section ld joined together by a safety joint or collar i3 has arranged about it a slip housing 14.

The upper, outer periphery of mandrel .section l2 is provided with a lug 15 and a sealing means such as a packing ring i6.

A valve sleeve vi7 is slidably arranged about the upper mandrel section l2 and is as shown threadedly connected to a tubing or operating string 18 which extends to the earths surface and connects to a hoisting means not shown. The inner wall of valve sleeve i7 is provided with a J slot i9 (see FIG. 3) which operabiy engages with the lug l5 on mandrel section l2.

Valve sleeve ll7' is provided with at least one port 2i) and the slip housing is provided with ports 2l. Ports Zit and 21, sleeve 17, and packing i6 together serve as a circulating valve for controlling fluid flow between the interior of mandrel l@ and the annulus between the housing i4 and the casing 9. This circulating valve is open in its lowermost position as shown in FIG. 1 with the lower end of the sleeve 17 abutting the top of safety collar 13. Flow of fluid may occur upward through the mandrel 10 around the upper end of the upper mandrel section 12, down through the annular space between the upper mandrel section :12 and the interior of the sleeve valve 17 and out through lateral ports Ztl and 2l. When the sleeve is in its uppermost position as shown in PEG. 2, the valve is closed as the packing ring sealingly engages the surface 24- of sleeve i7 above port Ztl and shoulder 23 contacts shoulder 22 of the mandrel section l2.

Safety collar 13 is provided with an open bottom J slot 25 which operably engages a lug 246 formed on the inner wall of housing i4. Housing 14 is also provided with drag springs 14a which engage the wall of casing 9. Lug 26 and slot 2S control the operation of slips 27 which are mounted in housing 14. The slips 27 are moved in and out of the housing by a wedge member Z3 which is mounted about mandrel section l1 with its lower end extending out the lower end of housing 14.

A frangible sleeve 29 referred to as the lower tensio-n sleeve is threadedly connected into the lower end of the wedge member 28 and has an internally projecting shoulder which engages an annular shoulder 30 of mandrel section ll. As can be seen, the shoulder 3u prevents upward movement of slip wedge 28 with respect to the mandrel section ll. As shown in FlG. l, the thin upper wall section of wedge 23 abuts against the bottom of safety collar i3.

An upper packer shoe 31 is mounted about mandrel 11 and the tension sleeve `29 and is retained against the -lower end of wedge 28 by a pair of packer sleeves 32 and 33 which are separated lby a metal ring 34. The sleeves 32 and 33 are held in place by shoe 31 and a lower shoe 35 which -s threadedly connected to mandrel section 11 as shown. I

Upper packer sleeve 32 is formed of a somewhat rm resilient material such as 95 durometer rubber while the lower sleeve 33 is formed of a softer material such as 75 durometer rubber. This arrangement affords a more elhcient seal when the sleeves are compressed and squeezed against the casing wall. The more firm sleeve 32 acts as a back-up for the softer sleeve 33.

As ycan be seen, the upper end of housing 14 is provided with a second tension sleeve 40 which forms a shoulder -41 and which is adapted to be engaged by a shoulder 42 of collar 13.

The upper tension sleeve 40 is designed to part or shear at approximately 30,000 pounds pull and the lower tension sleeve 29 at 100,000 pounds pull.

Operation The assembly is lowered into the casing 9 by means of the tubing 18 to the desired depth at which the packer as-i sembly lis to be set. The vario-us parts will assume the position as shown in FIG. l. The drag springs 14a contact the wall of casing 9 with a force sufficient to support the housing 14 and prevent its rotation and vertical movement while the mandrel is manipulated within it.

The tool is run in with the circulation valve assembly in the open position, but the valve is not necessarily locked open. The sleeve 17 being connected to the operating string 18 pushes against the upper end of the safely collar 13. The shoulder 30 and the collar 13 prevent the wedge 28 from pushing out on the slips 27. The lug 26 is in the locked position as shown in FIG. 4.

The tubing 1S is now rotated to the right, unlocking the circulating valve and the J lug 26. The pipe is picked up and the circulating valve is closed as the packing ring 16 engages lthe surface'24 of valve sleeve 17. Shoulder 23 is now contacting shoulder 22 and lug 15 is positioned in the long porti-on of the slot 19.

Continued upward pull on tubing 18 moves the mandrel 10 upwardly and `the wedge 28 forces the slips 27 intoV gripping contact with the Wall of casing 9 as shown in FIG. 2. When the slips 27 are set to `the extent that they prevent further upward movement of fthe wedge 28, the packer sleeves 32 and 33 then begin to compress and further pull on tubing 18 causes them to be squeezed against the easing wall between the shoes 31 and 35 until they afford an effective seal between the mandrel and the easing.

The assembly is now in position whereby a treating fluid can be pumped down the tubing 18, through the mandrel 10 and into the icasing 9 below the packer assembly. As the pressure of ithe cement being pumped in increase's,'aV greater force is applied to the wedge 28'causing the slips 27 to bite deeper into the pipe wall.

When it isdcsired to retrieve the -assembly'8, the tubing 18 `is lowered, opening the circulating valve and the'valve sleeve 17 abuts against ythe top of safety collar 13`. The tubing is rotated to the left which places the lugs in the locked position in their respective slots. The safety co1- lar and shoulder 30has forced the wedge 28 down out of contact with .the slips 27 so that they can retract into the housing 14. The assembly is now in position to be removed from the well casing.

Now, if the treating fluid pumped through the assembly were in the form of a cement slurry and allowed to set in the casing as shown .in FIG. 2, the lower end of the assembly may be cemented in so that -it is stuck. The

hardened cement also affords an obstacle against downward movement of the mandrel when it is desired to release :the tool.

Cil

It is not possible to now retrieve the assembly in the normal manner as previously described, as the mandrel 10 cannot be moved down with respect to the slip housing 14. This is the sor-t of situation for which the upper and lower tension sleeves are provided.

The tubing is rotated tol the right until the safety joint is disconnected from the lower mandrel section 11. The lug may or may not be in the locked position in slot 19. After the safety joint 13 has been backed off, the pipe is picked up until the shoulder 42 of collar 13 comes up against the shoulder 41 of the upper tension sleeve 40. This raises the housing 14 and therefore raises the slips 27 out of contact with the wedge 28 allowing the slips to be retracted.

A pull is then lapplied to the tubing which is transmitted to the shoulder 41 `of upper tension sleeve 40. lf the tool is not -too tightly cemented in `the entire assembly can now be retrieved. A jarring action may be attained by reciprocating the tubing 13 causing shoulder 42 to move upwardly, striking shoulder 41. Should the tool be rmly ycemented in and Ithe force applied exceed 30,000 pounds, the upper tension sleeve will part or shear and the mandrel section 12, circulating Valve sleeve 17, and the safety sleeve can be removed with the tubing 18.

Should the tension sleeve 40 part and the upper portion of the tool be removed, the inner wall of the extended housing 14 provides a neck which can now be engaged by a fishing and pulling ltool schematically shown as 45 in FIG. 7. An upward pull is then again applied to the tubing 18 which is connected to the pulling tool 45.

The pull now applied `can be anywhere in the range of 30,000 pounds to 100,000 pounds. During this pulling operation, the remainder of the assembly previously left in the casing may then `be pulled loose and removed.

However, should the pulling force exceed 100,000 pounds, Vthe lower tension sleeve 29 will then part or shear and the housing 14, `along with the slips `and wedge, can then be removed, leaving the lower portion 11 of mandrel 10 and the packer sleeves 32 and 33 in the casing. The `upwardly extending section 11 of the mandrel 10 now affords a neck that can be easily engaged by another fishing tool. The portion left in the casing as shown in FG. 7 may be iished out or may be drilled up or may, if desired, be left in the casing.

Referring now to FIG. 8, the tool illustrated has been somewhat modified with respect to the other FIGS. l through 7. The upper tension sleeve 40 is here replaced by an upper safety sleeve 50 which is threaded into the upper end of the housing 14 as shown. The lower end of the sleeve is provided with spaced apart clutch teeth 5l. The upper end of safety collar 13d is lalso provided with clutch teeth 52. The remainderV of the tool is identical to that of the previous tool and like parts are identified with like numerals.

If the tool is not stuck or 4cemented in, the normal releasing procedure is the same as in the other modification.

Should the tool, however, be stuck, the safety collar 13a is backed olf .and the teeth S2 raised by the tubing 18 into contact with the teeth 51 of the sleeve 50. A predetermined pulling force Yis then applied against the sleeves()V to try and pull the assembly 8 loose.

Should this not -be suiicient to pull the tool loose, the tubing 18 may be reciprocated so as to use the collar 13a as a hammer against the bottom of the sleeve 50 to jar the assembly loose. yIf this still does not loosen the assembly, the tubing is pulled up and rotated so that the teeth 52 operably engage the teeth 51 and the upper safety sleeve v50 -is backed off out of the housing 14. The same parts as shown in FIG. 6, along with the safety sleeve 50, can now be removed. The remainder of the assembly is then removed in the same manner as previously described with respect to the FIGS. l through 7.

It can be seen by the foregoing description and the drawings that the present invention affords a tension packer that can be set by upward movement of the oper-` ating string or tubing and be released by downward movement of the operating string.

The tool also provides means whereby the tool may be released by upward movement of the operating string, as well as downward movement.

The upper and lower tension sleeves provide means for removing the assembly a portion at a time, should the tool become stuck or cemented in during well treating orations.

The present invention also provides an |assembly t0 which a reciprocating hammer action can be applied by the tubing in Ian effort to release the tool by jarring, should it become stuck or cemented in.

Having fully described and illustrated the advantages `and operation of the device of the present invention, what is claimed is:

l. A packer assembly adapted to be suspended on the lower end of a pipe string and positioned in a well casing, comprising in combination: an elongated cylindrical housing provided with means for frictionally engaging the wall of said casing, spaced apart slips extending through windows in the wall of said housing, a hollow mandrel coaxially aligned with and extending through said housing, said mandrel comprised of an upper section and a lower section releas'ably connected together by `a safety collar fixed to the lower end of said upper section above said slips, a releasable locking means releasably connecting said safety collar to the wall of said housing, a valve sleeve having a lateral port therein, said valve sleeve being slidably arranged about said upper mandrel section and operably engaging therewith for limited vertical movement thereo-n, the upper end of said valve sleeve adapted to be connected into the lower end of said pipe string, said upper mandrel section closing said port in its uppermost position and opening said port in its lowermost position, a slip operating member slidably arr-anged on said lower mandrel section and formed to bias said slips outwardly upon upward movement of said member relative to said slips, the lower end of said member eX- tending out the lower end of `said housing, a frangible tension sleeve connected to the lower end of said member and operably engaging said lower section whereby upward movement of said member relative to said mandrel is prevented while upward movement of said mandrel relative to said member is allowed, a deformable packer sleeve positioned about said lower mandrel section and extending from the lower end of said member to au annular plate fixed to the lower end of said mandrel, said packer sleeve being expandable radially into contact with said well casing upon upward movement of said mandrel relative to said member, a removable sleeve member threaded into the upper end of said housing for limiting the `upward movement of said upper mandrel section when said mandrel sections are disconnected, said assembly providing an axial bore therethrough.

2. An assembly as in claim l in which said means for frictionally engaging the wall of said casing are drag springs.

3. An assembly as in claim l in which said releasable locking means comprises in combination an open bottom J slot formed on the outer wall of said collar operably engaging a J lug on the inner wall of said housing.

4. An assembly as in claim l in which said removable sleeve member is a frangible tension sleeve formed to part when a predetermined upward pull is exerted against it by the said safety collar.

5. A packer assembly adapted to be suspended on the lower end of a pipe string and positioned in a well casing comprising in combination: a Ihollow mandrel comprised of an upper section and a lower section releasably conneoted together by -a safety collar fixed to said upper section, a valve sleeve having a circulating port therein, said valve sleeve being slidably arranged about and extending above said upper mandrel section and operabiy engaging said upper mandrel section yfor limited vertical movement thereon, said upper mandrel section `closing said circulating port in said sleeve in its upper position and opening said port in its lower position, said valve sleeve adapted to connect by its upper end to said pipe string, a cylindrical housing arranged about said mandrel and provided with friction means for engaging the wall of said casing, a plurality of pipe gripping slips arranged in windows in said housing, a releasable locking means connected between said safety collar and the inner wall of said housing, a wedge shaped sleeve positioned in said housing below said slips and slidably arranged ion said lower mandrel section, the lower end of said wedge shaped sleeve extending below said housing, the wedge surface of said sleeve `facing so as to bias said slips outwardly upon upward movement of said wedge shaped sleeve in sa-id housing, a frangible sleeve arranged about said lower mandrel section and connected to the lower end of said wedge shaped sleeve, the lower end of said -frangible sleeve pr-oviding an internally projecting annular shoulder adapted to engage the underside of an annular shoulder on said lower mandrel section, an upper annular shoe member arranged about said lower mandrel section and abutting against the lower end of said wedge shaped sleeve, a lower annular plate txed to the lower end of said lower mandrel section, a deformable packer means arranged about said lower section yand extending between said plate members, said packer means being expandable into contact with said well casing upon upward movement of said lower mandrel section relative to said wedge shaped sleeve, a removable means connected into the upper end of said housing for limiting the upward movement of said upper mandrel section when said sections are disconnected, said removable means adapted to operably engage the said safety collar.

6. An assembly as in claim 5 .in which said safety collar is provided with spaced `apant clutch teeth on an annular upward facing shoulder thereon and said removable means is a sleeve threadedl-y connected into the upper end of said housing Iand provided with spaced apart clutch teeth about the lower end thereof, said teeth of said collar 4and said sleeve operably engaging when said sections are disconnected whereby rotation of said collar by said pipe string will unscrew said sleeve from said housing.

7. An assembly as in claim 5 in which said deformable packing means is comprised of an upper sleeve and a lower sleeve separated by an annular ring, said lower sleeve formed of a deformable material of lesser durometer ith-an said upper sleeve.

8. An assembly in accordance with claim 5 in which said friction means are drag springs.

9. An assembly as in claim 5 -in which said removable means is a tension sleeve adapted to limit the upward movement of said upper mandrel section when said mandrel sections are disconnected, said tension sleeve formed to pant when a predetermined upward p-ull less than that required to part said frangible sleeve is exerted `against it by said safety collar and said pipe string.

10. A tension packer assembly adapted to be carried on a pipe string and positioned within `a well casing, comprising in combination: a housing having friction drag means adapted to engage the casing, wedge slips carried on said housing and movable into engagement with the casing, deformable packer means below said housing expandable into contact with the casing, a tubular mandrel extending through said housing and said packer means and having an upper section `and a. lower section, a safety collar xed on said upper section and threadedly connected to said lower mandrel section, shoulder means on the lower mandrel section supporting said deformable packer means, a slip expander cone slidably on said lower mandrel section and between said deformable packer means and said wedge slips, whereby upward movement of said mmdrel relative to said housing is effective to expand said Wedge slips into engagement with the casing, means whereby said upper mandrel section may be carried by a pipe string, and frangible means including a sleeve element onl said housing engageable -by said safety collar following threaded disconnection [thereof yfrom said lower mandrel section and subsequent lifting of said upper-mandrel section by said pipe string.

l1. A tension packer assembly ladapted to be carried on a pipe string Iand positioned within a wellcasing, comprising in combination: a housing having lateral windows and having friction drag means adapted to engage the casing, wedge slips in said windows movable into engagement with the casing, deformable packer means below said housing expandable into contact with the casing, ya 'tubular mandrel extending through said housing and said packer means and having an upper section and a lower section, a safety collar fixed on said upper section and -threadedly connected to said lower mandrel section, shoulder meansv on the lower mandrel section supponting said deformable packer means, releasable control means on the housing `and safety collar for limiting relative axial movement mherebetween, a slip expander cone slidably on said lower mandrel'section and between said deformable packer means and said Wedge slips, whereby upon release of said `control means upward movement of said mandrel relative to said housing is elfective to expand said wedge slips into engagement with the casing, means whereby said upper mandrel ysection may be carried by a pipe string, and frangible means including a sleeve elment on said housing engageable by said safety collar following threaded disconnection thereof from said lower mandrel section and subsequent lifting of said upper mandrel section by said pipe string.r

12. A tension packer assembly adapted to be carried on -a pipe string and positioned within a well casing, comprising in combination: a housing having friction S. drag means ladapted to engage the casing, wedge slips carried on said housing and movable into engagement with fthe casing, deformable packer means below said housing expandable into contact with the casing, a tubular mandrel extending through said housing and said packer means and having an upper section and la lower section, a safety collar fixed on said upper section and threadedly conneoted to said lower mandrel section, shoulder means on the lower mandrel section supporting said deformable packer means, a slip expander cone slidable on said lower mandrel section and beltween said deformable packer means and said wedge slips, whereby upward movement of said mandrel relative to said housing is elfective to expand said Wedge slips into engagement with the casing, means whereby said upper mandrel section may 'be carried by a pipe string, a frangible sleeve element on said housing engageable by said safety collar following threaded disconnection thereof lfrom said lower mandrel section and subsequent lifting of said upper mandrel section by said pipe string, an ,abutment on the lower mandrel section, a frangible sleeve connected to said slip expander cone and having a portion thereof underlying said abutment, `and cooperating means on the housing Iand expander cone whereby the housing m-ay lift the expander cone to apply a tension force to the latter said frangible sleeve.

References Cited in the le of this patent UNITED STATES PATENTS 2,368,399 Baker Ian. 30, 1945 2,633,201 Clark Mar. 31, 1953 2,704,126 Davidson Mar. 15, 1955 2,715,442 Brown Aug. 16, 1955 2,849,025 Conrad Aug. 26, 1958 

1. A PACKER ASSEMBLY ADAPTED TO BE SUSPENDED ON THE LOWER END OF A PIPE STRING AND POSITIONED IN A WELL CASING, COMPRISING IN COMBINATION: AN ELONGATED CYLINDRICAL HOUSING PROVIDED WITH MEANS FOR FRICTIONALLY ENGAGING THE WALL OF SAID CASING, SPACED APART SLIPS EXTENDING THROUGH WINDOWS IN THE WALL OF SAID HOUSING, A HOLLOW MANDREL COAXIALLY ALIGNED WITH AND EXTENDING THROUGH SAID HOUSING, SAID MANDREL COMPRISED OF AN UPPER SECTION AND A LOWER SECTION RELEASABLY CONNECTED TOGETHER BY A SAFETY COLLAR FIXED TO THE LOWER END OF SAID UPPER SECTION ABOVE SAID SLIPS, A RELEASABLE LOCKING MEANS RELEASABLY CONNECTING SAID SAFETY COLLAR TO THE WALL OF SAID HOUSING, A VALVE SLEEVE HAVING A LATERAL PORT THEREIN, SAID VALVE SLEEVE BEING SLIDABLY ARRANGED ABOUT SAID UPPER MANDREL SECTION AND OPERABLY ENGAGING THEREWITH FOR LIMITED VERTICAL MOVEMENT THEREON, THE UPPER END OF SAID VALVE SLEEVE ADAPTED TO BE CONNECTED INTO THE LOWER END OF SAID PIPE STRING, SAID UPPER MANDREL SECTION CLOSING SAID PORT IN ITS UPPERMOST POSITION AND OPENING SAID PORT IN ITS LOWERMOST POSITION, A SLIP OPERATING MEMBER SLIDABLY ARRANGED ON SAID LOWER MANDREL SECTION AND FORMED TO BIAS SAID SLIPS OUTWARDLY UPON UPWARD MOVEMENT OF SAID MEMBER RELATIVE TO SAID SLIPS, THE LOWER END OF SAID MEMBER EXTENDING OUT THE LOWER END OF SAID HOUSING, A FRANGIBLE TENSION SLEEVE CONNECTED TO THE LOWER END OF SAID MEMBER AND OPERABLY ENGAGING SAID LOWER SECTION WHEREBY UPWARD MOVEMENT OF SAID MEMBER RELATIVE TO SAID MANDREL IS PREVENTED WHILE UPWARD MOVEMENT OF SAID MANDREL RELATIVE TO SAID MEMBER IS ALLOWED, A DEFORMABLE PACKER SLEEVE POSITIONED ABOUT SAID LOWER MANDREL SECTION AND EXTENDING FROM THE LOWER END OF SAID MEMBER TO AN ANNULAR PLATE FIXED TO THE LOWER END OF SAID MANDREL, SAID PACKER SLEEVE BEING EXPANDABLE RADIALLY INTO CONTACT WITH SAID WELL CASING UPON UPWARD MOVEMENT OF SAID MANDREL RELATIVE TO SAID MEMBER, A REMOVABLE SLEEVE MEMBER THREADED INTO THE UPPER END OF SAID HOUSING FOR LIMITING THE UPWARD MOVEMENT OF SAID UPPER MANDREL SECTION WHEN SAID MANDREL SECTIONS ARE DISCONNECTED, SAID ASSEMBLY PROVIDING AN AXIAL BORE THERETHROUGH. 